Hi Sonji,
Yes, you can convert Publisher and other files to PDF by using a free PDF converter tool that acts as a "PDF printer" on your computer.
PrimoPDF is one that I recommend for you (there are other free ones too, like CutePDF).
After you install PrimoPDF, follow these steps (quoted from the product's Web site) to convert your file to PDF:
[olist][*]In the document-authoring program (in your case, Publisher), select File > Print.[/*]
[*]Select the PrimoPDF printer from the choices of available printers and click OK.[/*]
[*]The Create PDF window appears. Enter a name and select a location for the PDF file.[/*]
[*]Select whether the PDF will be used for Screen, Print, EBook or Prepress.[/*]
[*]Click Security to access the security settings window.
NOTE: Security settings are optional. See the Security section for details.[/*]
[*]Click Document Properties to enter a brief description of the PDF.
NOTE: Document Properties are optional. See the Document Properties section for details.[/*]
[*]Click Save.
NOTE: By default, the PDF will be opened in your default PDF viewer upon completion. You can change this behavior in the PrimoPDF program options. Refer to PrimoPDF Program Options for additional details.[/*][/olist]
Hope this helps!
Yann